In response to PAR-14-304, NIMH Mentoring Networks for Mental Health Research Education, this application seeks five years of support to build, maintain, and sustain an innovative mentoring network for implementation science in mental health. This network will extend in creative new ways the Implementation Research Institute (IRI, NIMH R25 funding 2009-2015), which has successfully trained 43 new mental health implementation researchers. Implementation science is critical for mental health where most Americans with mental disorder receive sub-optimal care due in large part to challenges in the implementation, sustainability, and scale-up of evidence-treatments. Training demand far outweighs supply but only a handful of programs train implementation researchers and only the IRI in mental health. Therefore we seek a one-time, five-year renewal of IRI to pursue three aims: to (1) develop a mentoring network of faculty and Fellows who will advance the science and lead the field of mental health implementation research; (2) evaluate outcomes of the IRI mentoring network, inform continued improvement to training, and derive new knowledge about the role of mentoring networks in accelerating collaboration, scholarly productivity and research training; and (3) extend training benefits to the broader field by disseminating lessons learned, training models, and tools for creating sustainable mentoring networks. To achieve aim 1, we will conduct an innovative, continually renewed annual summer institute; foster networked collaboration and mentoring; prepare IRI Fellows to mentor others in their home institutions, thus extending and sustaining IRI's reach and impact; and use learning visits to federally funded implementation research sites to help Fellows connect IRI training to team based, real-world science. Evaluation methods will include bibliometrics and social network analysis, with outcomes including mentoring effectiveness, collaboration, and scholarly products (publications and grant proposals). IRI will provide innovative training at the forefront of implementation science to 24 new researchers (six in four two-year cohorts). New Fellows will be networked with past Fellows, Core Faculty, and Expert Faculty to spur collaboration and foster scholarly innovation. Their research will accelerate innovation in the implementation science and inform sustainable improvements to mental health care-thereby reducing the burden of mental illness for countless individuals and families. IRI Fellows will be well prepared for Three T Science--team, translational, trans-disciplinary-called for by the Investing in the Future report (National Advisory Mental Health Council Workgroup on Research Training). Fellows will advance the field through their scholarship and will lead the next generation of implementation researchers in mental health. Objectives of the NIMH strategic plan cannot be achieved without advances in implementation science for mental health, where disease burden is high, the repertoire of effective treatments is growing, but availability and receipt of evidence- based care is low.